1. Field of the Invention
The invention relates to the field of vapor production and distribution. It may find more specific use in the field of wind tunnel flow visualization.
2. Description of the Related Art
Applications for vapor production can be found in a variety of fields. In theater settings vapor may be produced as a visual special effect. For training exercises vapor production may serve to simulate a fire. Yet another use is in wind tunnel airflow visualization.
In wind tunnel airflow visualization, a model is placed in a low speed wind tunnel, an airflow is provided and the interaction between the airflow and the model is observed. In order to render visible the motions of the air the experimenter provides what is known as a smoke plume, in practice this is not usually smoke but rather a vapor created by heating an oil or other substance until a vapor is produced. The resulting vapor is not the product of combustion so is not properly called a smoke. The plume of vapor, when properly illuminated provides the experimenter with a visible indication of direction of airflow in a given region.
It is desirable to be able to provide the vapor without disturbing the natural airflow of the observed system. It is also often desirable to be able to move the source of vapor to various points in the wind tunnel so that airflows around different portions of the model may be observed.
The currently available selection of vapor producing devices does not meet the needs of the airflow visualization community. These devices tend to be bulky, having a heater, liquid reservoir, and controlling electronics contained in one device. In general, they produce a low density smoke stream. They may be unsuitable for use in airflow visualization due to the downwind effects produced by airflow around the generator itself. While these effects may be diminished by careful selection of test geometry, that step will necessarily reduce the tester's ability to move the vapor source.
Parrish (U.S. Pat. No. 3,964,304) discloses a compact smoke generator for use in airflow visualization. This device makes use of a heating element with the fluid heated in a coil wrapped around the heating element.
Weinstein (U.S. Pat. No. 4,493,211) discloses a smoke generator that makes use of a heating tube that is closed on one end and has an output hole drilled through a portion of the heating tube's sidewall. Weinstein specifically addresses the problem of producing a compact generator that is capable of producing laminar flow.
Each of these devices is capable of producing a vapor that may be used for airflow visualization. Each is more compact than prior art devices, however both must still be employed at a distance from the area of interest in testing because they still have somewhat bulky bodies.
It is an object, therefore, of the present invention to provide a vapor generating device that causes minimal interference with airflow in the region surrounding the device.
It is a further object of the present invention to provide a device that may be easily relocated within a wind tunnel.
Another object of the present invention is to provide a device that is easily scalable so that it may be employed in a wide range of wind tunnel situations.